a. Field of the Invention
The invention relates to gas lasers and more particularly, to a pulsed gas laser construction.
b. Prior Art
After the discovery of the nitrogen laser in 1963 by H. G. Heard, it was realized that the initial longitudinal tube configuration was too inductive and that the laser medium was too long to excite its entire length during the short lifetime of the laser transition. This realization prompted work on transversely excited discharges which have very low inductances and utilize shorter discharge paths, see D. A. Leonard, App. Phys. Letters 7, 4 (1965). This approach raised the laser peak pulse output power, eventually to megawatts.
While the transversely excited nitrogen laser shows a vast improvement in efficiency over the first longitudinally pumped nitrogen laser, it suffers from two main drawbacks. First, the output beam is in the shape of a line transverse to the direction of light propagation, and second, the excitation tube would be difficult to operate in a sealed off mode, because of the need for seals along the full length of the laser tube.
Efforts have continued to improve longitudinally excited nitrogen lasers, and laser tubes have been developed with low inductance, coaxial construction, moderate discharge lengths, usually under 30 centimeters, and spark gap switching. For example, see U.S. Pat. No. 3,458,830 granted July 29, 1969 to Geller. There are numerous constructions for longitudinally excited nitrogen lasers in the prior art. These structures are generally coaxial with spark gas switching and are complex and inconvenient for assembly or replacement of the laser tube. Most of these structures ignore the problem of heat dissipation from the laser tube and the few that recognize the problem are too complex to be commercially useful. Finally, relatively few of these structures have been reported to operate with the gas laser tube sealed off, and those that do, use spark gap switching or have other undesirable features, such as laser pulse power decreasing as repetition rate is increased.
The spark gap switches in these prior art longitudinally excited lasers are undesirable because they must be dismantled and cleaned periodically. They are more susceptible to pulse jitter and are difficult to operate in a sealed off mode.
Accordingly, it is an object of the present invention to provide a low inductance, longitudinally excited, pulsed gas laser which allows for improved heat conduction from the laser tube, can operate in a gas flow mode or in a sealed off mode, with output power essentially independent of repetition rate, is compatible with thyratron switching, is relatively simple to fabricate and has a tube and thyratron which are easily replaced.